Contribution of optical phonons to thermal boundary conductance

Thermal boundary conductance (TBC) is a performance determinant for many microsystems due to the numerous interfaces contained within their structure. To assess this transport, theoretical approaches often account for only the acoustic phonons as optical modes are assumed to contribute negligibly due to their low group velocities. To examine this approach, the diffuse mismatch model is reformulated to account for more realistic dispersions containing optical modes. Using this reformulation, it is found that optical phonons contribute to TBC by as much as 80% for a variety of material combinations in the limit of both inelastic and elastic scattering.